WEBVTT

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SLOS TRXI is an x ray
imager used on OMEGA. It is a

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fixed diagnostic mounted onto
the system at Port h four and is

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only removed once a year for
routine maintenance. Anytime it

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is removed or re installed onto
the system, experimental

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technicians must work cleanroom
suits, which helps protect the

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entire Omega system from dust
and debris. TRXI is capable of

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taking multiple frames with a 40
picosecond temporal resolution

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at a 10 micron spatial
resolution. This is achieved by

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combining an electron pulse
dilation imager with a fast

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gated sensor. It captures X rays
in a four to nine KV range

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around the time of peak
compression during ICF. SLOS

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TRXI is used to determine the
size of the core of imploded

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cryogenic targets at stagnation.
This allows for the inference of

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the hotspot pressure.

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The imager on SLOS TRXI is a
pinhole array, about 30 images

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of the hotspot can be obtained
per frame, and these individual

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pinhole images are average to
increase the signal to noise

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ratio.

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The photons are then incident on
the photocathode and produce

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electrons via the photoelectric
effect. The photocathode is a

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transmission photocathode where
photons are incident on one side

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and electrons lead from the
other side.

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To colliding high voltage pulses
travel across the photocathode

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and some to create a spatially
uniform voltage profile. The

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photocathode voltage varies in
time, and the kinetic energies

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of the electrons are time
dependent. So electrons that are

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born earlier in time have a
higher velocity than electrons

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born later in time.

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The electron cloud then enters
the drift region which is held

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at a constant potential. The
electron cloud elongates as it

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travels down the drift tube due
to the differing velocities.

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There is a solenoid around the
drift tube to produce an axial

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magnetic field that prevents the
transverse spread of the

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electron cloud. Due to the high
voltages in the imaging system,

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the drift tube is held at a high
vacuum to prevent electrical

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arcing.

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The electrons are detected on
multiple frames of an HC MOS

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sensor, which is a 2d detector
developed at Sandia National

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Laboratories. The detector is
time resolved, with about a 2.5

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nanosecond gate time per frame.
Coupled with the drift tube,

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which has a temporal
magnification of about 80 times

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the effective gate time is
approximately 35 to 40 pico

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seconds.

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Here's an unprocessed readout of
the H CMOS sensor. You can see

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the images are changing in time
getting brighter from frame one

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to frame to. The individual
pinhole images are then cut out

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and added together to create a
composite image. On the right is

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how the image compares one to
510 and 29 separate images are

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included in the stack

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SLOS TRXI is the second time
resolved X ray imager used on

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OMEGA a third time resolved X
ray imager is currently being

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designed and will operate
similarly to SLOS TRXI. This

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third line of sight will have
approximately a 20 picosecond

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temporal resolution and a five
micron spatial resolution.

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The three time resolved X ray
images will be used together to

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help us understand how the
hotspot evolves in time, the

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multi dimensional effects that
occurred during ICF implosions

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and to create a 3D
reconstruction of the hotspot